Manufacturers of semiconductor chips and assemblies use automatic test equipment (“ATE”) to verify device functionality and performance. These manufacturers preferably test semiconductor chips as early as possible in the manufacturing process to avoid the costs of processing defective devices. A device called a “prober” holds unpackaged chips for testing by the ATE. A device called a “handler” holds packaged chips.
ATE systems typically include a “test head.” The test head houses potions of the ATE that are preferably located as closely as possible to the device under test, and connects to a main body of the ATE via one or more cables. To test a device, the test head is “docked,” or secured, with the prober or handler, and the ATE tests the chip.
Constraints affecting semiconductor testing make it impractical to move the chips to the test head. In most modern manufacturing facilities, the prober or handler that holds the chips remains stationary, and the test head is moved to dock with the prober or handler.
The ATE moves the test head to the prober or handler using a device called a “manipulator.” Manipulators must satisfy a complicated and difficult set of requirements. First, the manipulator must be able to handle heavy test heads. Test heads for high performance ATE can weigh hundreds, or even thousands, of pounds.
Also, the manipulator must be able to change the orientation of the test head to enable the test head to dock with a wide range of prober/handlers. Some prober/handlers require that the test head be positioned vertically, and others require that it be positioned horizontally. Still others require that the test head be oriented at an angle between horizontal and vertical.
The manipulator must provide “compliance” about various axes of rotation. “Compliance” is the range of rotation over which a test head can be adjusted, to dock the test head with the prober/handler once the manipulator places the test head approximately in position. Achieving compliance is particularly difficult if a test head is heavy, as the manipulator must be well balanced and have low enough friction to allow fine adjustments to be made.
The manipulator also must fit in the physical space available on the test floor. ATE systems generally integrate with existing test facilities, many of which have extremely limited available floor space. As test heads grow and become increasingly heavy, manipulators tend to grow proportionally. Frequently, little room is available on the test floor to accommodate the growth of the manipulator.
Prior manipulator designs have attempted to address this difficult set of requirements by providing parallel fork arms for holding a test head from its sides. According to these designs, the test head includes an adapter on each side for receiving one of the manipulator's fork arms. The fork arms join behind the test head and form a single shaft. The manipulator can lift the shaft to adjust the height of the test head, and rotate the shaft to adjust the angle of the test head. Each fork arm includes a rotational bearing coupled to the respective adapter on each side of the test head. The rotational bearings enable the test head to rotate in an up-down, or “tumble,” direction (described below).
For heavy test heads, the fork arms of the manipulator become exceedingly thick. The heavier the test head, the thicker the fork arms must be. In addition, the fork arms generally include mechanical parts that provide compliance about various axes of rotation. Larger mechanical parts are generally required for larger test heads, and the fork arms become thicker still. Thick fork arms interfere with neighboring equipment, and conflict with the requirement that the manipulator fit within the available space on the test floor.
Moreover, the fork arm manipulator uses distinct sets of mechanical parts to achieve compliance about different axes of rotation. For example, rotation about the “theta” and “tumble” axes (described below) is provided by parts within each of the two fork arms. Rotation about the “twist” axis (described below) is provided by parts coupled to the shaft behind the test head. Requiring different parts at different locations within the manipulator to achieve compliance adds complexity to the manipulator and, again, takes up additional space.
With the foregoing background in mind, its an object of the invention to provide a manipulator that takes up relatively little space even when used with heavy test heads.
Another object of the invention is to provide compliance for a test head about different axes of rotation in a relatively simple manner.
To achieve the foregoing objects and other objectives and advantages, a manipulator includes an elongated blade that extends along a central axis from a region outside of a test head into an internal region of the test head. The manipulator includes an interface coupling disposed in the internal region of the test head. The interface coupling has a first portion coupled to the elongated blade and a second portion coupled to the test head. The first and second portions of the interface coupling are free to rotate with respect to each other in compliance about at least one axis of rotation.
In accordance with another embodiment of the invention, a manipulator includes a stiffener fixedly attached to the test head and having top, bottom, and back portions. An elongated blade extends into an internal region of the test head between the top and bottom portions of the stiffener and in front of the back portion of the stiffener. The manipulator includes an interface coupling that has a first portion coupled to the elongated blade and a second portion coupled to the stiffener. The first and second portions of the interface coupling are free to rotate with respect to each other in compliance about at least one axis of rotation.
In accordance with another embodiment of the invention, a method of assembling a test head for use with a manipulator includes providing a stiffener having top, bottom, and back portions. The method includes inserting an elongated blade into an internal region between the top and bottom portions of the stiffener and in front of the back portion of the stiffener, and attaching the elongated blade to the stiffener. The method also includes fastening respective first and second portions of the test head to left and right mounting surfaces of the stiffener.
Additional objects, advantages and novel features of the invention will become apparent from a consideration of the ensuing description and drawings.